1. Field of the Invention
The present invention relates to a refrigerant compressor and a refrigerating apparatus. More particularly, the invention relates to a refrigerant compressor and a refrigerating apparatus using at least a refrigerant selected from the group of hydrofluorocarbon-based refrigerants or a mixed refrigerant formed by mixing two or more refrigerants selected from the group, i.e., an HFC-based refrigerant in place of the conventional CFC-based or HCFC-based refrigerants containing chlorine.
2. Description of the Related Art
In a conventional refrigerant compressor composing a refrigerating apparatus, a plain bearing made of a material comprising a surface layer containing lead bronze, a resin such as PTFE and a lead component for improving slidability is usually used in a sliding section engaging with a driving shaft of the compressor or an engaging section with a stationary member rotatably supporting the driving shaft.
On the other hand, R-12, a CFC-based refrigerant containing chlorine, and R-22, an HCFC-based refrigerant, have been used as a refrigerant. As compared with sulfur dioxide and methylchloride, refrigerants used therebefore, these conventional refrigerants are chemically more stable, less toxic and non-flammable. They had therefore been popularly employed as ideal refrigerants. More recently, however, chloride contained in the CFC-based and HCFC-based refrigerants were found to destruct the ozone layer of the stratosphere, and there is an urgent demand for the development and use of a new refrigerant taking the place of these conventional refrigerants. Highly practicable new refrigerants taking the place of the CFC-based and HCFC-based refrigerants include hydrofluorocarbon (HFC)-based refrigerants not containing chloride.
Because a refrigerating lubricant is discharged from a compressor, carried by the flow of the refrigerant in the refrigerating apparatus, and circulated in the compressor, the oil should have misciblity with the refrigerant. Mineral oils and alkylbenzene oil used as conventional CFC-based or HCFC-based refrigerants have a very low misciblity with the above-mentioned HFC-based alternative refrigerants. It is therefore conceived to use an ester oil miscible with the alternative refrigerants.
However, when an HFC-based refrigerant, an alternative refrigerant, and an ester oil, a refrigerating lubricant, are combined and used, and the compressor is based on a combination of a plain bearing comprising a material containing lead, lead contained in the material of the bearing precipitates in the refrigerating lubricant, thus resulting in deterioration of the refrigerating lubricant. Deterioration of the refrigerating lubricant leads to a poorer lubricity of the sliding portions such as the bearing section, this further causing wear and galling of the sliding portions and hence a decrease in reliability.
Also in the case where the compressor has a rolling bearing, the rolling bearing receives a very high load on a limited small load bearing surface. The lubricant fed to the load bearing surface of the rolling bearing therefore locally receives a very high pressure. An ester oil has a far smaller viscosity under a high pressure than a mineral oil and a low oil film forming ability on the load bearing surface. The ester oil was thus found to suffer from wear and galling of the sliding portions, leading to a lower reliability.